Underfeed stoker



Dec. 8, 1936.

e M. SEAMAN 2,063,347

UNDERFEED STOKER Original Filed April 21, 1935 G/LBE/Q 7' M Sci/WW INVENTOR ATTORNEY Patented Dec. 8, 1936 PATIENT OFFICE 2,063,347 UNDERFEEl) STOKEB Gilbert M. Seaman, Catskill, N. Y.

Original application April 21, 1933, Serial No. 667,245. Divided and this application January 22, 1935, Serial No. 2,857 I f 2 Claims. (Gl. 110-45) This is a division of my co-pending application, Serial Number 667,245, filed April 21, 1933.

My invention relates to mechanical underfeedv stokers for coal-burning furnaces and the like;

and it has for its objectto provide dependable means for preventing discharge of gases of combustion (hopper smoke) from the furnace by way of the fuel-feed conduit and thence through the fuel hopper to the ambient atmosphere.

10 In furnaces equipped with mechanical underfeed stokers of the character here dealt with, the coal or other solid fuel is delivered from a hopper through a fuelvfeed conduit, by means of -a feed screw, to the bottom of a retort and thence upwardly through the retort wherein combustion occurs. I

Due to the fact that air for combustion is delivered to the burning fuel through the perforated wall of the retort and meets with some little resistance in its passage to the flue, and to the further fact that the air is supplied at a pressure above atmospheric, there is a continuous tendency for a back-draft to flow from the interior of the retort through the fuel feed conduit and 5 thence through the fuel hopper to the atmosphere about the furnace. carries with it some of the gaseous products of combustion (unless adequately provided against) and isfor that reason both a nuisance and. a 30 menace to health. As hereinbefore stated,,the

present invention is designed to prevent the discharge of such gases other than by way of the flue.

It has previously been proposed, as for ex- 35 ample in U. 8. Patent Number 1,876,310 to Jacob Madlehner, to introduce into the fuel stream a supply of uncontaminated air under suitable pressure for the purpose of creating a barrier to the gas-laden, air which would otherwise be discharged through the fuel-feed conduit and hopper. The principle thus previously expounded is thoroughly sound and is the one underlying the present invention; but the devices and arrangements heretofore proposed for carrying it into 45 eifect have in each instance, so far as I have been able 'to learn. been insuflicient, from a practical standpoint, because of susceptibility to becoming.

clogged and thus rendered inoperative by accumulations of coal dust; and no adequate pro- 50 vision hasbefore been suggested whereby such obstructions could readily be removed.

In the stoker construction of the present invention the auxiliary air'duct through which the auxiliary air supply is delivered to the fuel-stream 55 for the P p se of establishing a gas barrier is so This back-draft frequently designed and disposed that it does not readily become clogged; and, what is of comparable importance, means are provided whereby this duct can easily and conveniently be cleared by the furnace attendant.in event it does, in the course of 5 time, become clogged. i

A preferred embodiment of my invention is illustrated in the accompanying drawing where- Fig. 1 is a vertical sectional view of a portion 0 of an underfeedstoker together with the retort or flrepot and tuyere chamber-only such parts being shown as are necessary to adequately disclom,

the invention;

Fig. 2 is a plan view with certain parts broken 15 away in order more clearly to show the inventive features; and

Fig. 3 is a cross-sectional view of the fuel-feed conduit and auxiliary air duct, taken along the line 3-3 of Figs- 1 and 2. 20 I The structure illustrated comprises, as its major components, an iron casting I, approximately in the form of an inverted truncated cone having a circular lateral opening at 2; a cast iron elbow 3 mounted inside the casting l; a retort or flrepot 4, ordinarily of cast iron, mounted within the casting I, its upper end resting on the upper flange of casting l and its lower end on the upper face of elbowl; a tubular fuel-feed conduit 5, one end of which projects into the elbow 3; a fuel-feed screw inside the fuel-feed conduit, but not shown in the drawing; and a clean-out-rod 6 having a plunger head 1 and handle 8.

The casting I together with elbow I and retort 4 form, conjointly, a tuyere chamber ,9 which surrounds the retort and serves as a conduit for air under pressure above atmospheric which is thus delivered to the interior of the retort through a large number of small openings therein, identified as a group by reference'numeral I ll. 40 Air under pressure is provided by a suitable blo er, not shown. which is connected to the tuyere chamber through the medium of a conduit II and manifold I 3.

The fuel, which is generally coal of-small size, such as buckwheat or rice, is fed slowly by the fuel-feed screw from a fuel hopper, not shown, through the fuel-feed conduit 5 and thence through elbow 3 and upwardly through the retort wherein combustion takes place.

In operation, the retort is filled to overflowing with burning fueland ashes, fresh fuel constantly moving up from the bottom and air for combustion being introduced under pressure above atmospheric through the numerous openings Ill.

I It is manifest that the forced draft will carry the greater part of the gaseous products of combustion upwardly to the flue; but it will be apparent, upon reflection, that a part of the draft, after entering the firebed, will tend to pass-downward ly through the elbow 3 and out through the fuelfeed conduit and hopperand that such discharge as might occur in that manner would carry with it some noxious fumes-that being the problem with which the present invention is concerned. v

By introducing uncontaminated air under sum cient pressure into the fuel-feed passageway, in advance of the firebed, as, for instance, into the elbow 3, a barrier may-be created to the flow of gas-laden air from the flrebed through the fuelfeed conduit and hopperthe air thus injected into the fuel-feed passageway creating an upward draft in opposition to the down-draft of gas-laden,

air. Thus it follows that the only flow oi air finding its way out of the fuel hopper by way of the fuel-feedconduit is that of the auxiliary sup-' ply which is without contamination and there- ;fore unobjectionable.

In the structure illustrated there is provided an auxiliary air duct I! which, as will be seen, is outside of the fuel-feed conduit and extends in the same direction as the flow of fuel from the fuel-feed conduit and arranged to discharge air into the fuel stream at the point of discharge of fuel from the conduit and in the same direction as the flow of fuel from the conduit. I have found that with the auxiliary air duct thus arranged there is never any discharge of gas through the hopper and there is a minimum of tendency for the duct to become clogged and the auxiliary air supply thus cut oil.

It will be observed that the auxiliary air duct opens at its intake end into a manifold chamber i3 which is a passageway for the forced draft being delivered to the tuyere chamber and that I the air suppliedto the auxiliary air duct is accordingly'at the same pressure as that in the tuyere chamber or, perhaps, a little higher.

The auxiliary air duct l2 arraiigedas here illustrated and described exhibits a marked tendency to remain continuously free of obstruction; but as an added precaution I have provided means ciently smaller than the duct I! so that the flow of: air isnot unduly impeded.

To clear the duct II of obstruction or to make certain that it is not obstructed, the furnace attendantsim'ply moves the cleanout rod in and out a few times by means of the handle 8.

What I claim is: v

1. In an underfeed stoker, the combination with a hopper, a retort and a fuel-feed conduit conne'cting said hopper and retort, of means defining a tuyere chamber surrounding said retort, an auxiliary air duct for delivering air under pressure above atmospheric to the fuel stream in advance of said retort, a source of air under pressure above atmospheric connected with said tuyere chamber and auxiliary air duct, and a manually reciprocable cleanoutrod extending from the exterior of said stoker into said auxiliary air duct and operable upon manipulation to clear said auxiliary air l defining a tuyere chamber surrounding said re-N tort, a source of air at a pressure in excess of atmospheric connected with said tuyere chamber, an auxiliary air duct connected with said source 'cf air and arranged to discharge into the fuel stream at a point below said retort, and a cleani out rod extending from the exterior of said stoker into said auxiliary air duct, said cleanout rod hav-- ing a plunger head fitting loosely in said auxii, iary air duct so as not to, interfere substantially with the flow of air through the duct, said plunger head being operable upon reciprocation of said cleanout rod to free the auxiliary air duct of any obstructive matter whichmay have accumulated therein.

GILBERT M. SEAMAN. 

